The present invention relates to an apparatus for handling a control rod driving mechanism of a nuclear reactor. More particularly, the invention is concerned with an improvement in an apparatus for mounting and demounting, at the time of periodical inspection of a nuclear reactor, the control rod driving mechanism on and from a housing attached to the pressure vessel of a nuclear reactor, as well as for transporting the control rod driving mechanism to and from a place suitable for inspection and maintenance.
The control rod driving mechanism (referred to as "CRD", hereinunder) has to be demounted and then mounted at the time of periodical inspection of the nuclear reactor. The handling of CRD essentially requires a suitable countermeasure for reducing the radioactive dosage, because the work for handling CRD has to be done in an atmosphere of a high rate of radioactive dosage.
The specification of U.S. Pat. No. 4,292,133 discloses an apparatus for replacement of CRD. This apparatus has a CRD mounting/demounting means and a CRD transporting means which are constructed separately, such that the replacement of the CRD is conducted by cooperation between these two means. These two means are equipped with respective trucks for carrying the CRD. In order that the cooperation between these two means can be conducted satisfactorily, it is essential that the trucks of both means are aligned with each other at a high precision. In the replacement of CRD, it is necessary to operate a mast driving mechanism such as to horizontally lay down the mast in advance to the transportation of the CRD to and from the mounting position. This in turn requires the CRD mounting/demounting means to clear the mast because the mast has a large length. The replacement of the CRD which is disposed in the peripheral region of the reactor and, hence, closest to a pedestal, requires the greatest care in order to avoid any risk of interference between various equipments and pipes on the pedestal wall and the CRD mounting/demounting means of the apparatus when this means is retracted in advance of the horizontal laying down of the mast. To avoid this risk, hitherto, a visual check or observation of the clearance between the pedestals and the CRD mounting/demounting sections by the operator has been necessary.